Negative attitudes towards insects, such as fear and disgust, are often a result of human-insect conflicts. Although only about 10,000 insect species are considered as serious or sporadic pest species (Meyer, 2006), their negative impacts, coupled with media sensationalism, could lead to a generalisation of all insects being treated as pests. This section presents various examples of the impacts of insects as agricultural pests, disease vectors and nuisance species.
Agricultural pests
According to the FAO, herbivorous insects are responsible for destroying a fifth of the global crop production yearly. The presence of insect pests is fuelled by the conversion of natural habitats to large agroecosystems, where nutritious crops of large sizes and high yield are concentrated in one area and creates a favourable environment for insect infestations (Sallam, 1999). A famous example is the Colorado potato beetle, Leptinotarsa decemlineata. This species was first documented as a pest of potato crops in eastern Nebraska, USA, in 1859, where there were multiple hectares of potato fields throughout the eastern states of America (Casagrande, 1987).
The swarming of desert locusts in East Africa is a more recent example that is also driven by ideal conditions associated with crop harvest seasons and shifting wind patterns (Marks, 2020). The current locust invasion has been considered as East Africa’s “worst extended infestation in 25 years”, where more than 400,000 hectares of land have been destroyed by the swarms (Howes, 2020).
Disease vectors
Blood-sucking insects are common disease vectors that transmit disease-causing parasites, viruses and bacteria from an infected to a new host (WHO, 2020). The bubonic plague (or black death) is transmitted by fleas and killed more than a third of Europe’s population between the 14th and 17th century (Cockburn, 2020). Currently, malaria and dengue are the most prevalent vector-borne diseases that are transmitted by mosquitoes, and result in about 219 million and 3.90 billion yearly cases respectively (WHO, 2020).
Nuisance insects
Other insect species neither cause significant agricultural damage nor are disease carriers. They also do not inflict injury but are still considered as annoying or nuisance species (Meyer, 2006). Most examples involve swarms of these insects around a vicinity or entering households, and could be triggered by changing seasonalities and weather patterns.
In Singapore, residents staying in the vicinity of a reservoir were disturbed by swarms of midges that disrupted their daily lives and even affected nearby food establishments (Ang, 2019). Numerous complaints have compelled government authorities to conduct various management measures, such as regular fogging, greasing drain walls to trap midges, and releasing fishes into the reservoir as a form of biological control (Today, 2019).
